Add ability to interrupt the process

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This may only work on Posix systems, but it would be nice to have. See Calysto/matlab_kernel#5.

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I couldn't get it working. It is hard to separate the zmq server from the Matlab instance. I tried allowing the zmq server to restart from either or both ends of the connection, but nothing would cooperate.

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This may be of use: http://stackoverflow.com/a/21314664

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The above addresses the python end, but there appears to be no way to recover the Matlab/Octave end after an interrupt.

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Closing as stale.